Video imagery coming out of Ferguson, Missouri has been dramatic over the past week, but the still photos have also defined coverage of this international story. One photo in particular caught the eyes of many people.

SCOTT OLSON: My name is Scott Olson. I'm a photojournalist. I work with Getty Images.

VIGELAND: The photo, taken on Tuesday, shows a young black man in a light blue shirt and baseball cap standing on a sidewalk - his hands raised above his head. Facing him, a group of police officers - 10 of them in the frame - wearing camouflage, gas masks and pointing their weapons directly at the young man. We asked Olson to describe what was happening when he captured that moment.

OLSON: There were protesters gathered at the corner, and there'd been some skirmishes earlier, but at that point there was just milling about. And then police just kind of randomly - at least I didn't see any provocation - but they started firing with the rubber bullets. And one of my colleagues, she got hit, and she looked at me and she said, I just got hit, and then you could smell the tear gas. So people started scrambling, and basically I was backpedaling, trying to make pictures as you're running out of the chaos. And I'd seen this person standing there, being confronted by the police and the police were trying back him down, and he was trying to hold his ground, and - just made the frame.

VIGELAND: Scott Olson shot the photo in the chaos on the run. He couldn't see what happened to the young man. And it wasn't until later when he realized what he had captured.

OLSON: You don't see everything at that moment. In fact, I didn't even realize how heavily harmed those police were until I started doing my edit later.

VIGELAND: The result was a scene shared countless times online, in newspapers is in the U.S. and around the world. Olson is also a former Marine, and the scenes in Ferguson surprised him as he's taken photos of police staring down rifle scopes on the street.

OLSON: I think it's crazy. I think they really don't understand why they have M-16's out there, why they have sniper rifles out there. Most of these protesters are peaceful, and if you have one or if you have several people that are trying to disrupt the protest, you're not going to shoot at them with a rifle - not in a crowd like that. I mean, this is one main business district that is flanked by a residential neighborhood. A rifle - you just don't know where that round's going to stop.

VIGELAND: Olson was out covering protests again last night. He thought he would head back to his home in Chicago earlier in the week, but that was before this story took a much different turn. Transcript provided by NPR, Copyright NPR.